CommonProxy preInit:
Call this for every block:
        GameRegistry.register(b);
		ItemBlock i = new ItemBlock(b);
		ModelLoader.setCustomModelResourceLocation(i, 0, new ModelResourceLocation(s, "inventory"));
		GameRegistry.register(i.setRegistryName(b.getRegistryName()));

ClientProxy init:
Call this for every block:
		Minecraft.getMinecraft().getRenderItem().getItemModelMesher()
	    .register(Item.getItemFromBlock(block), 0, new ModelResourceLocation("TestMod:" + block.getUnlocalizedName().substring(5), "inventory"));

Model file for block:
add the "parent": "block/block" line

Model file for item:
{ "parent": "block/theblockname" }
literally it